1. Field of the Invention
This invention relates to a cooling system for a V-type engine transversely mounted on a motor vehicle.
2. Description of the Prior Art
In a motor vehicle with a transversely mounted V-type engine, a radiator is disposed at the front of the engine as viewed in the longitudinal direction of the vehicle, with the radiation surface thereof arranged nearly perpendicularly in relation to the longitudinal direction of the vehicle, such that outside air will hit the radiation surface nearly perpendicularly during travel. That is, the radiator is installed on the side of the engine with the radiation surface thereof being nearly in parallel with the axis of an engine crankshaft. Therefore, there is a problem that various members of the cooling system, such as a water pump and a thermostat, are arranged in a space provided on the side of the engine, and accordingly it is impracticable to manufacture compact engines. Furthermore there also is a problem that because an exhaust system and other systems are disposed on the side of the engine, the cooling system interfered with such systems, resulting in a difficult layout of the cooling system on the side of the engine. To cope with these disadvantages, there has been proposed a cooling system for the V-type engine wherein the water pump and the thermostat are mounted at the end section of the engine (hereinafter referred to simply as "the engine end section") as viewed in the axial direction of the crankshaft.
In the conventional cooling system for the transversely mounted V-type engine, as shown for example in FIG. 1, a water pump 41 is mounted at the front end of an engine 40; a thermostat 42 is disposed at the rear end; and a suction line 44 communicating with a radiator 43 and the suction port of the water pump 41 is arranged through the thermostat 42 and a V-like space between the banks 45 and 46 of cylinders of the engine. The coolant is supplied to the engine 40 from the water pump 41 through coolant supply lines 47 via coolant inlet ports 48. This coolant is returned to the radiator 43 through a coolant return line 51 via coolant outlet ports 49 provided at the rear end of the engine 40. Furthermore, there is provided a bypass line 52 for returning the coolant to the suction line 44 by bypassing it through the radiator 43 when the coolant temperature is low. A part of the coolant is supplied also to a driver's seat heater 55 through a coolant line 54 for the heater.
Furthermore, in a conventional cooling system as shown in FIG. 1, since the water pump 41 and the thermostat 42 are not mounted on the side of the engine 40, a much larger space is provided at the side of the engine 40, thereby preventing interference between these devices and the exhaust system. However, because of the presence of the coolant return line 51 and the bypass line 52 on the side of the engine 40, it is still impossible to make the engine substantially compact.
Furthermore, with a recent increase in the number of drivers who are fond of low-hood vehicles, the production of low-hood vehicles has been demanded. In conventional cooling systems, the radiator to be mounted in a position where the height of the hood should be held to a minimum extends largely in a vertical direction in order to improve the cooling efficiency, with the result that the hood can not be substantially lowered.
Besides the above-described conventional art, a technique is known in the prior art (Laid-Open Japanese Utility Model No. 61-128335) for providing the coolant inlet port in one end of the engine body for leading the coolant into the engine, disposing the coolant outlet port in the other end of the engine body, and positioning a communication line connecting the outlet port to the radiator in a space between the radiator and the engine body. According to this technique, however, the space required for mounting the cooling system increases in the direction the width of the engine.